Range controller circuits are used to monitor the frequency of a clock generated by a phase lock loop (PLL). A range controller circuit ensures that the phase lock loop has an output clock with a frequency within an acceptable range. Typical range controller circuits have a reference clock that is compared to the recovered clock from the phase lock loop. The range controller has a master counter coupled to reference clock and a sample counter coupled to the recovered clock. When the difference between these two counters is too large, a link fault indicator flag is set. One problem with typical range controllers is that the latch for the link fault indicator signal is clocked by the reference clock. If the reference clock is unavailable, the link fault indicator signal does not latch. As a result, the range controller may indicate an incorrect status for the link.
Thus there exists a need for a range controller that does not require the reference clock to be active to provide accurate state information.